The invention pertains to on-line monitoring of one or more physical properties of a free flowing product such as a granular or particulate material. Examples of properties to be monitored are moisture content, temperature, color, etc. An example of a process where on-line monitoring is employed is in the manufacture of animal feed. When an analytical procedure or device is adapted for on-line monitoring of a manufacturing process, one of the most difficult problems encountered is the presentation of the monitored material to the sensor. For the on-line assay to have any meaning, what the sensor xe2x80x9cseesxe2x80x9d must accurately represent the monitored process in real time. The physical characteristics of free flowing particulate materials compound the basic problems encountered when placing an on-line sensor in a process stream. Any attempt to divert or restrict the particulate flow invites plugging or bridging. Particulate flow patterns are seldom uniform since augers and bucket elevators are commonly used to move these materials, giving the flow pattern a pulse. The particles themselves are frequently of irregular shape and size. Some particulates may be fragile and can easily be damaged or destroyed by rough sampling techniques. Some particulates because of their size and shape have difficulty moving under the influence of gravity through a sampling cell. Such materials require special attention.
In some installations it is necessary to retrofit the process stream equipment with a property sensor. This can present a problem with finished ductwork. Access to the process stream for installation of a sensor and sensor cell may be difficult. Consideration must be given to the intrusion into the process stream by the process sensor equipment.
The invention relates to an on-line sensor mount assembly for monitoring material properties of a free flowing process stream. The sensor mount assembly can readily be installed in new or pre-existent ductwork of a processing installation. The sensor mount assembly includes an open ended housing. A side wall of the housing can be flat and of suitable length and width to function as a mounting plate for installation of the housing in an opening formed in a duct wall of a duct system. Side walls of the housing define an unobstructed passage sensing chamber for free flowing particulate material. One or more material property sensor elements can be installed on one or more of the side walls. The housing has an upper inlet opening and a lower outlet opening. The housing passage is uniform from top to bottom to facilitate the free flow of particulate material and minimize clogging and bridging. A metering element of a variable speed flow metering apparatus is located in blocking relationship to the housing outlet. Operation of the flow metering element transports material through the outlet at a regulated rate. Regulating the product flow rate through the housing outlet permits control of the flow rate past a material property sensor associated with the housing. This control assures a uniform flow rate through the passage. The motive force or motor to move the metering element is located remote from the process stream duct. In one embodiment, the metering element is a brush that rotates near the outlet opening, transporting product from above it to below it. In another embodiment, the metering element is a conveyor belt; in another it is a screw conveyor; and in yet another it is a pulse or jet of air.